I just read about Trapit over on the ProfHacker blog and had to give it a try myself to see how it compares to other alert/feed tools. Unlike an RSS reader, Trapit allows you to search for a topic (set a trap), and then it snags articles from around the web on that topic. Then, you can fine-tune your trap by giving articles a thumbs up or thumbs down Pandora-style, so that no two traps are exactly alike.
I joined a couple of popular shared traps on "Big Data" and "Digital Textbooks" and then set traps for some of my subject areas and found some interesting articles I would not have stumbled across otherwise. So far, I'm finding that it's a good way to take the current pulse of a topic and to see what's out there that you might have missed, but it's no replacement for my RSS reader in terms of keeping track of news sites and blogs that I know I want to see everything from.
I do appreciate the way Trapit is laid out visually, and they have an iPad app coming out soon. Here is a screen shot from my Food Science trap.